Gas-Phase Alloying and Sintering Kinetics of 3D Printed Ni Scaffolds

几何形状日益复杂的金属零件的制造引起了许多行业的兴趣。特别是，金属支架由于其低密度和高表面积，从电池到生物医学植入物的各种应用都是很好的候选者。然而，许多技术上重要的合金很难用传统的制造方法在支架几何形状中制造出来，即使是新的方法，如增材制造（通常被称为3D打印），也面临着重大挑战。理论上，一种新的工艺可以通过两步法制造这些金属支架，这将使从相同的前体打印金属部件中生产各种不同的材料成为可能。该奖项支持对控制这一新过程的动力学和热力学基本机制的研究。由于金属支架结构的工程应用范围广泛，本研究的结果将促进许多制造业的技术创新，包括能源、汽车和生物医学行业。通过招募和推广活动，传统上在STEM中代表性不足的群体将参与到这项研究工作中来，这将使学生在很小的时候就参与进来，并有助于使工程职业管道多样化。虽然粉末床增材制造技术能够制造具有高几何复杂性的近净形状金属部件，但由于烧结不良、内部孔隙和开裂，许多工程相关合金难以高质量制造。一种替代方法是通过使用基于颗粒的油墨印刷来分离印刷和合金，从已知可以成功打印的纯金属或简单合金中创建所需的几何形状，然后使用沉积过程和均质化在单独的步骤中进一步合金零件以达到目标成分。这种方法是制造金属支架的理想方法，利用了开放孔隙度和小扩散距离的优势。该项目的总体目标是利用常规金相学和原位x射线层析显微镜相结合的方法研究这种支架的基本烧结和合金化动力学。相和孔隙演化将作为几何形状、成分、粉末和支撑尺寸、退火时间和温度的函数进行系统研究，力学行为将通过计算预测和实验确定。

The fabrication of metal parts with increasingly complex geometries is of interest to several industries. In particular, metal scaffolds are good candidates for a variety of applications from batteries to biomedical implants, due to their low density and high surface area. However, many technologically important alloys are difficult to fabricate in scaffold geometries using traditional manufacturing, and even newer approaches such as additive manufacturing (often known as 3D printing), have significant challenges. A new process has been theorized for making these metal scaffolds through a two-step approach, which will enable an assortment of different materials to be produced from the same precursor printed metal part. This award supports research to understand the fundamental mechanisms of kinetics and thermodynamics that control this new process. Because of the wide range of engineering applications for metal scaffold structures, results from this research will promote technological innovations in a number of manufacturing sectors including energy, automotive and biomedical industries. Through recruiting and outreach activities, traditionally underrepresented groups in STEM will be involved in this research effort, which will engage students at an early age and help diversify the engineering career pipeline.While the ability to create near-net-shape metallic parts with high geometric complexity has made powder-bed additive manufacturing techniques attractive, many engineering relevant alloys are difficult to fabricate with high quality due to poor sintering, internal porosity, and cracking. One alternative approach is to decouple the printing and alloying by using particle-based ink printing to create the desired geometry from a pure metal or simple alloy that is known to print successfully, and then further alloy the part in a separate step using a deposition process and homogenization to reach the target composition. This approach is ideal for creating metallic scaffolds, taking advantage of the open porosity and small diffusion distances. The overall aim of this project is to study the fundamental sintering and alloying kinetics of such scaffolds using a combination of conventional metallography and in situ X-ray tomographic microscopy. The phase and pore evolution will be systematically studied as a function of geometry, composition, powder and strut size, and anneal time and temperature and the mechanical behavior will be computationally predicted and experimentally determined.